Block-signal system.



L. A. HAWKINS.

BLOCK SIGNAl. SYSTEM.

APPLICATION FILED JUNE 6,1908. RENEWED APR. 28. 19H.

Patented June 20, 1916.

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BLOCK SIGNAL SYSTEM.

APPLICATION FILED JUNE 6.1908. RENEWED APR. 28. 19m.

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BLOCK SIGNAL SYSTEM.

APPLICATION FILED JUNE 6, 190s. RENEWED APR.28. 1911.

1 88,273. Patented June 20, 19161 3 SHEETS-SHEET a;

I 1 1 WITNESSES, JNYENTUR \A (g IAUHEZSTDE A. HAWKINS.

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LAURENCE A. AwKins, or sc msewam, ronic assIGnoasY MEsnE Assmn ENTs ro THE UNION swr'rcn AND SIGNALCOMPANY, A oonronA'rion 0F PENN;

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specification of Letters Patent. Pate ted Jane 20, 191;;

Application filed June e, 1908, Serial to. 437,065. Renewed A'p'ri128, 1911. Serial No. 623,969.

To all whom it may concern: 7

Be it known that I, LAURENCE A. HAW- KINS, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New Yorl have invented certain new and useful Improvements in Block-Signal Systems, of which the following is a specification;

My invention relatesto block signal systems for railways like the ordinary electric railway, having both rails 'conductiv'ely continuous for all currents, and its object is to provide an efficient, reliable and simple signal system for use on such roads.

In a prior application, Serial No. 435,861, filed June 1, 1908, I have explained how the skin effect in a rail traversed by alternating current may be utilized in a signal system by connecting the track relays in shunt to a short lengtl'i of rail. In that application all the sources of alternating current connected to the rails were of the same frequency and phase and closed paths for the signal current were formed by impedances across the rails between the sources. In my present system the sources themselves form the only connections across the rails, and adjacent sources supply currents of different character, so that two adjacent sources with the rails between them form a closed circuit traversed by a resultant current made up of the two component currents furnished by the two sources, respectively. As will hereinafter be explained, the difference in character of the currents supplied by adjacent sources may consist in diflference in phase or in frequency.

While, in my former application, I disclosed relays each having a track winding composed of two coils connected in shunt to two short lengths of rail opposite each other in the track, so that the power current in the two relay coils produced opposing effects, I pointed out certain advantages from the omission of one of those coils in that particular system, and disclosed as a preferred form, and claimed, the one-coil arrangement. In my present system the two-coil arrangement possesses the advantage above mentioned as to the effect of power current, and does not introduce any limitation, as in the former system. I consequently include as one feature of my pres ent invention the two-coil arrangement of the track windings of the relays.

My invention will best be understood by reference to the accompanying drawings, in which' Figure 1 shows diagrammatically a block signal system arranged in accordance with mylnvention; Fig. 2 shows a modification of the same, having two frequencies in place of two phases supplied to the track circuits; and Fig. 3 shows a modification of the arrangement of Fig.- 1, in which two relays per block are employed.

In Fig. 1, A represents the track rails, which may be continuous throughout their length, as in an ordinary electric railway. B represents a two phase generator, which supplies the current for the signal circuits.

I have shown a three-wire transmission system supplied from this generator, the wire 6 serving as common return for both phases; one phase being connected between the wires 1) and b andthe other phase being connected between the wires 6 and 6 C, C and C represent transformers having their primaries connected to the transmission system and their secondaries connected across the rails through impedances 0. These impedances, which may be either inductive or non-inductive, serve to limit the current drawn from a transformer when a train stands on the track at the transformer. Adjacent transformers have their primaries connected to different phases of the trans mission system. D and D represent relays, which are shown as of the well known twophase induction type, comprising a movable short-circuited secondary member (l, carrying the relay contacts, and two sta tionary coiiperating windings (Z and d The winding (Z preferably is composed of two coils, as shown, connected across two short rail lengths opposite each other in the track, and adjacent to one of the transformers. A second winding (Z of the relay is supplied independently of the track circuits by connection to the transmission wires througli a suitable phase controlling means indicated by the resistance (Z E and E represent signals controlled by the track relays.

i (Z received from transformer C the ends of the block. These two currents are displaced from each other ninety degrees in phase, so that the resultant current is displaced in phase forty-five degrees from each component current. The winding (Z of the relay D is supplied from the same phase as the supply transformer C, and the resistance d is so adjusted that the current in the relay winding (Z is substantially in phase with the component current in the track windings (Z receivedfrom the transformer C. The current in winding (Z of relay D is thus ninety degrees out of phase with the current component received in winding al from transformer C Consequently, the current in winding d cooperates only with the component current in winding With this adjustment of the phases of the currents in the relay windings, it will be seen that a train approaching the block guarded by signal E the direction of traffic being as indicated by the arrow, will gradually shortcircuit transformer C, but Will not thereby affect the relay torque, since its only effect on the current in the track winding is gradually to remove the component current received from transformer C, which component produces none of the relay torque. With the front wheels of the train directly over transformer C, the track winding of relay D is receiving only current from transformer G which is the current which actuates the relay. As soon as the front wheels of the train have passed over the short rail lengths (50 or 100 feet, for instance) spanned by the relay track winding, the

relay is totally deenergized, and the signal E goes to danger. The point at which the signal goes to danger is thus defined within the short rail length spanned by the track winding of the relay. As long as the train is in the block, the current from transformer C is cut off from relay D and this relay remains deenergized since it cannot be cleared by current from transformer C, which is of the wrong phase to operate it, and any current which may come from the transformer next beyond transformer C will tend merely to hold the relay more firmly in stop position. This can best be seen by considering the effect of a train between transformers C and C Any current from transformer C, passing transformer C will flow in the opposite direction through winding (Z of relay D from that in which the current from transformer C flows. Consequently, its effect is to give the relay a counter-torque, holding it in its deenergized position.

The advantage of employing two coils for winding d for the relays is twofold. First, since the power current flows in the same direction in both rails, it produces opposing effects in the two coils of the relay track winding; and second, for a given amount of current in the rails and a given torque to be obtained in the relay, the distance spanned by the relay need be only one-half as much, if both rails are utilized, as would be required if the relay winding were connected in shunt to only one rail. Consequently the entering point of the block is more definitely defined.

Since each relay is close to a transformer, to the current from which it must not re spond, it is essential that the current in the winding (Z2 of the relay should be carefully adjusted, so as to give either Zero torque or a small counter-torque, when the current in the track winding is supplied only from the adjacent transformer. Furthermore, the power factor of the impedance 0, in series with the secondary of the transformer, must be properly selected. If the power factor of this impedance is the same as that of the rails for the frequency employed, then the phase of the current delivered by the transformer is substantially the same when a train is in a block near the transformer, and when the block is clear. On the other hand, an impedance of such a power factor may be selected that with the block clear and the current from the transformer consequently flowing through the entire rail length of the block, the phase of the current delivered is such as to produce no torque in the relay; while with a train in the block close to the transformer, so that most of the rail impedance is out of circuit, the phase of the current delivered by the transformer is shifted so as to give a counter-torque in the relay adjacent to it.

If, instead of relying on a difference of phase in the currents supplied to the track by the transformers, a difference of frequencies is utilized, no careful adjustment of the relay is necessary, since, if the frequencies are properly selected, each relay will remain wholly unaffected by current, except that from the source to which it is intended to respond. Such an arrangement is shown in Fig. 2, in which two two-phase generators B and B", of difierent frequency, are employed for furnishing the signal current. I have shown a five-Wire transmission system having a common re turn I), one phase of one generator being connected between wires 1) and b and the other phase between Z) and b and the two formed by the secondaries of two adjacent transformers and the rails between them' a composite current formed of two component currents of different frequency. Transformers G and C are similarly connected as in Fig. 1. The relays have their track windings connected as in Fig. 1, while their other windings are connected to the phases of the generators not connected to the supply transformers. Thus, relay winding (1 of relay D has impressed upon it a voltage substantially in quadrature to that impressed upon the track by transformer C and consequently the relay responds to the current from that transformer. Similarly, the corresponding winding of relay D has impressed upon it a voltage in quadrature to that impressed upon it by the transformer C With the two-frequency arrangement of Fig. 2, it is practically essential to employ separate transmission wires for supplying the windings (Z of the track relays, since the secondary of each track transformer has flowing through it a current of another frequency than that of the voltage impressed upon its primary, and this current induces a corresponding frequency in the primary, so that if the windings (Z were supplied from the same circuits as the primaries of the track transformers, the winding d of each relay would lHUe impressed upon it a composite voltage comprising a small component voltage of the frequency to which the relay is not intended to respond. Vith the separate circuits shown in Fig. 2, however, each relay is rendered absolutely independent of all currents except the one to which it is intended to respond.

One reason why it is necessary to adjust the phase of. the current in the winding (Z carefully in the arrangement of Fig. 1, is that this relay is so much closer to the source of current to which it is not intended to respond than it is to the source of current to which it should respond, so that because of track leakage, the resultant current flowing through the relay windings has a component current to which it should not respond greater than the component current to which it'should respond. This disadvantage does not exist in the arrangement of Fig. 3, in which the relays are placed midway between two adjacent sources. This arrangement, however, requires two relays per block, as is shown in the drawing. The transformers are placed in the centers of the blocks, and adjacent transformers are connected to different phases of the transmission system, as in Fig. 1. A relay is employed at each end of each block, the relays D and D having their contacts connected in series to control the signal E which guards the length of track between the relays. Fig. 1, are connected to the other phase The track windings (P, as in' from that to which the primary of the transformer to which they respond is connected. As in F ig. 1, each track circuit includes the secondaries of two adjacent transformers and the track rails between them.

The operation of the system will be evident from' the drawing and from the de scription that has already beengiven of Fig. 1. With a train between relay D and transformer C relay D is deenergiz'ed, while with a train between transformer C and relay D the latter is deenergized. The relays are unaffected by the train, until the front wheels of the train pass over the short rail lengths spanned by the relay track windings, so that the point at which the signal goes to danger is marked in precisely the same way as in the preceding figures. It will be noted, however, that there is a difference in regard to the definiteness with which the outgoing end of each block is defined. In Fig. l, for instance, the relay D does not clear the instant the rear wheels of the train have passed transformer C but remains deenergized until the train has passed transformer C a sufficient distance to enable the secondary voltage of the transformer to rise to an amount sufficient to send through the rail circuit between this transformer and transformer C acurrent of great enough amount to clear the relay D There is thus an overlap at the outgoing end of the block, which overlap is not absolutely definite. This overlap is not ordinarily a disadvantage, but, on the contrary, is an advantage, as affording additional protection. The arrangement of Fig. 3, however, defines the point at which the signal clears, as closely as the point at which the signal goes to danger is defined in all the modifications shown. The instant the back wheels of the train have passed from the short rail lengths spanned by winding (Z relay D is energized with its full torque, and consequently the point at which the signal clears is defined within the short rail length spanned by the relay track winding. This arrangement is, therefore, especially advantageous where an exact definition of the block is desired at the outgoing end, as well as at the incoming end. Such an exact definition is desired for cross-overs and interlocking.

Other combinations of transformer and relay connections will be obvious to those skilled in the art. Accordingly, I do not desire to limit myself to the particular connections and arrangement of parts here shown, but aim in the appended claims to cover all modifications which are within the scope of my invention. I

I do not in this application make any claim to a block signal system for railways having both rails conductively continuous for all currents, in which adjacent sources of current for the track circuits are of different character and the relays are selectively responsive to current of one character only, nor do I make any claim to a system for such railways having the relays arrails a closed circuit traversed by the resultant of the currents delivered by said sources, track relays each operatively related to one of said closed circuits and responsive only to the flow through said circuit of current from one of the sources comprised in said circuit, and signals controlled by said relays.

2. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating current connected at intervals across the rails, adjacent sources being of different character and forming with each other and the intervening rails a closed circuit traversed by the resultant of the currents delivered by said sources, track relays eachoperatively related to one of said closed circuits, each of said relays being adjacent to one source and responsive only to current flowing through said circuit from the source at the other end of said circuit, and signals controlled by said relays.

3. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating-current connected at intervals across the rails and forming the only electrical connections across the rails, adjacent sources being of diilerent character and forming with each other and the intervening rails a closed circuit traversed by the resultant of the currents delivered by said sources, track relays each having a winding connected in shunt to a short length of rail between two sources and responsive only to current from one source, said length of rail being suliicient to provide the drop in voltage necessary to energize the relay, and signals controlled by said. relays.

4-. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources 0]": alternating-current connected at intervals across the rails, adjacent sources being of different character and forming with each other and the intervening rails a closed circuit traversed by the resultant of the currents delivered by said sources, track relays each having a winding connected in shunt to a short length of rail between two sources and each of said relays being adjacent to one source and responsive to current from the other source only, said length of rail being sufficient to provide the drop in voltage necessary to energize the relay and signals controlled by said relays.

5. In a block signal system, in combina tion with a railway having both rails conductively continuous for all currents, sources of alternating-current connected at intervals across the rails and forming the only electrical connections across the rails, adjacent sources being of different character and forming with each other and the intervening rails a closed circuit traversed by the resultant of the currents delivered by said sources, track relays each having a winding connected in shunt to a short length of rail between two sources, said length of rail being sufficient to provide the drop in voltage necessary to energize the relay, and each relay having a second winding supplied independently of the track circuits with cur rent adapted to cooperate only with the current received in the track winding from one source to actuate the relay, and signals controlled by said relays.

6. In a block signal system, in combination with a railway having both rails conductively continuous for all currents, sources of alternating-current connected at intervals across the rails, adjacent sources being of different character and forming with each other and the intervening rails a closed circuit traversed by thev resultant of the currents delivered by said sources, track relays each having a winding connected in shunt to a short length of rail between two sources and each of said relays being adjacent to one source, said length of rail being suilicient to provide the drop in voltage necessary to energize the relay, and each relay having a second winding supplied independently of the track circuits with current adapted to cooperate only with the current received in the track winding from the other source to actuate the relay, and signals controlled by said relays.

in witness whereof, I have hereunto set my hand this 5th day of June, 1908.

LAURENCE A. HAWKINS.

lVitnesses BENJAMIN B. HULL, MARGARET E. lVooLLnY.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. 0." 

